What is ICD-10 code N17.1?

N17.1 is the ICD-10-CM diagnosis code for Acute kidney failure with acute cortical necrosis. Sudden loss of kidney function accompanied by death of the outer layer (cortex) of the kidney tissue. This is a severe form of acute kidney failure with significant tissue damage. N17.1 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. N17.1 is part of the FY2026 ICD-10-CM code set published by the CMS National Center for Health Statistics and used on Medicare, Medicaid, and commercial claims in the United States.

Yes. N17.1 is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. N17.1 is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

What is the V28 vs V24 difference for N17.1?

CMS phased in the V28 risk adjustment model over payment years 2024 (33%), 2025 (67%), and 2026 (100%), replacing V24. V28 consolidates HCC categories, removes some lower-acuity conditions, and recalibrates RAF weights across the entire model. N17.1 was a payment HCC under V24 (Acute Renal Failure) but the V28 recalibration removed it from the risk adjustment model. Both models can still appear in legacy data and in payer-specific lookback periods.

What should coders know when reporting N17.1?

This code indicates more severe kidney damage than tubular necrosis alone; document the underlying cause and severity Cortical necrosis often results from severe shock, sepsis, or severe hypotension; ensure the precipitating event is documented and coded Because N17.1 maps to a payment HCC, the documentation must also satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's risk adjustment score.

2026 ICD-10-CM N17.1: Acute kidney failure

ICD-10-CM Code View

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Code lookupN17.1Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Diseases of the genitourinary system (N00-N99) / Acute kidney failure and chronic kidney disease (N17-N19)

N17.1

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

Acute kidney failure with acute cortical necrosis

Sudden loss of kidney function accompanied by death of the outer layer (cortex) of the kidney tissue. This is a severe form of acute kidney failure with significant tissue damage.

Buddy Insight

Acute kidney failure with acute cortical necrosis represents severe kidney injury with death of the outer kidney tissue, indicating critical illness requiring immediate intervention.

CMS-HCC V28

N/A

—

Not risk-adjusted for this model/period.

Not mapped

CMS-HCC V24

Mapped

HCC 135

Acute Renal Failure

RAF 0.435

ACA/HHS

N/A

—

Not risk-adjusted for this model/period.

Not mapped

ESRD/PACE

Mapped

HCC 135

Acute Renal Failure

RAF 0.000

RXHCC

N/A

—

Not risk-adjusted for this model/period.

Not mapped

Code Book Path

Official

N17Acute kidney failure

N17.1Acute kidney failure with acute cortical necrosis

Inclusion Terms

Official

Acute cortical necrosis
Cortical necrosis NOS
Renal cortical necrosis

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for N17.1 in this effective period.

Related Child Codes

Official

N17.0Acute kidney failure with tubular necrosis

N17.2Acute kidney failure with medullary necrosis

N17.8Other acute kidney failure

N17.9Acute kidney failure, unspecified

Includes

Official

ICD-10-CM does not list Includes notes for N17.1 in this effective period.

Excludes 1

Official

posttraumatic renal failure (T79.5)

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for N17.1 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for N17.1 in this effective period.

Code Also

Official

associated underlying condition

Buddy Documentation Tip

HCC Buddy guidance

Acute kidney failure clearly documented with rapid onset

Evidence of cortical necrosis through imaging or biopsy

Laboratory values showing acute deterioration in kidney function

Documentation of precipitating factors or underlying causes

MEAT Support

HCC Buddy guidance

Acute kidney failure clearly documented with rapid onset

Evidence of cortical necrosis through imaging or biopsy

Laboratory values showing acute deterioration in kidney function

Documentation of precipitating factors or underlying causes

Audit Caution

HCC Buddy guidance

Using unspecified acute kidney failure codes when cortical necrosis is documented

Confusing cortical necrosis with medullary necrosis

Not documenting the acute nature versus chronic kidney disease

Failing to capture the severity indicated by tissue necrosis

Common Mistakes

HCC Buddy guidance

N17.2 — Acute kidney failure with medullary necrosis (different anatomical involvement)

N17.9 — Acute kidney failure, unspecified (lacks specification of cortical necrosis)

N18.6 — End stage renal disease (chronic rather than acute condition)

N19 — Unspecified kidney failure (not specifically acute with necrosis)

Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →

Is N17.1 an HCC code?

Yes. N17.1 maps to Acute Renal Failure under the V24 model but is not retained in V28.

Code: N17.1
Description: Acute kidney failure with acute cortical necrosis
HCC (V28): No CMS-HCC V28 mapping
RAF: —
Billable: Yes
Payment year: 2026

HCC Category Mapping

V24HCC 135, Acute Renal Failure

0.435

ESRDHCC 135, Acute Renal Failure

0.000

Each model's RAF is its CMS base weight for that model's standard population, so weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.

Work N17.1 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for N17.1

For N17.1 to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically, it has to be re-documented and supported each calendar year.

MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
EEvaluate: test results, medication response, or physical findings reviewed by the provider
AAssess: explicit mention in the assessment or plan with acknowledgment of status
TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis

Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed N17.1 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

N17.1 is the ICD-10-CM diagnosis code for acute kidney failure with acute cortical necrosis. Sudden loss of kidney function accompanied by death of the outer layer (cortex) of the kidney tissue. This is a severe form of acute kidney failure with significant tissue damage. N17.1 sits in the ICD-10-CM chapter for diseases of the genitourinary system (n00-n99), within the section covering acute kidney failure and chronic kidney disease (n17-n19).

Under the older CMS-HCC V24 model, N17.1 maps to Acute Renal Failure (HCC 135) with a community, non-dual, aged base RAF weight of 0.435. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.

This code indicates more severe kidney damage than tubular necrosis alone; document the underlying cause and severity. Because N17.1 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.

HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for N17.1 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•This code indicates more severe kidney damage than tubular necrosis alone; document the underlying cause and severity
•Cortical necrosis often results from severe shock, sepsis, or severe hypotension; ensure the precipitating event is documented and coded

Clinical Significance

Acute kidney failure with acute cortical necrosis represents severe kidney injury with death of the outer kidney tissue, indicating critical illness requiring immediate intervention. This condition has high mortality risk and significant impact on RAF scores due to its association with complex medical management needs.

Documentation Requirements

✓Acute kidney failure clearly documented with rapid onset
✓Evidence of cortical necrosis through imaging or biopsy
✓Laboratory values showing acute deterioration in kidney function
✓Documentation of precipitating factors or underlying causes
✓Treatment interventions including dialysis if applicable
✓Monitoring parameters for kidney function recovery
✓Assessment of fluid and electrolyte management needs

Commonly Confused Codes

•N17.2: Acute kidney failure with medullary necrosis (different anatomical involvement)
•N17.9: Acute kidney failure, unspecified (lacks specification of cortical necrosis)
•N18.6: End stage renal disease (chronic rather than acute condition)
•N19: Unspecified kidney failure (not specifically acute with necrosis)